Cutaneous manipulation of vascular growth factors leads to alterations in immunocytes, blood vessels and nerves: Evidence for a cutaneous neurovascular unit

Background

Skin cells produce soluble factors which influence keratinocyte proliferation, angiogenesis, nerve innervation and immunocyte response.

Objective

To test the hypothesis that epidermal-dermal interactions influence neural outgrowth, vascular survival, immunocyte recruitment and keratinocyte proliferation.

Methods

We genetically manipulated the epidermis to express excess vascular endothelial growth factor (VEGF) and/or angiopoietin-1 (Ang1) and then examined the epidermal and dermal phenotypes. We compared these findings with those occurring following overexpression of the Ang1 receptor Tie2 in endothelial cells or keratinocytes.

Results

Keratinocyte-overexpression of Ang1 resulted in increased epidermal thickness compared to control littermates. Keratinocyte-specific overexpression of Ang1 or VEGF increased dermal angiogenesis compared to control animals and combined Ang1-VEGF lead to further increases. Cutaneous leukocyte examination revealed increases in CD4⁺ T cell infiltration in mice with keratinocyte-specific overexpression of Ang1, VEGF and Ang1-VEGF combined; in contrast only keratinocyte-specific Ang1 overexpression increased cutaneous F4/80⁺ macrophage numbers. Interestingly, combined keratinocyte-derived Ang1-VEGF overexpression reduced significantly the number of F4/80⁺ and Cd11c⁺ cells compared to mice overexpressing epidermal Ang1 alone. Endothelial cell-specific Tie2 overexpression increased dermal angiogenesis but failed to influence the epidermal and immune cell phenotypes. Keratinocyte-specific Tie2 expressing mice had the highest levels of CD4⁺, CD8⁺ and CD11c⁺ cell numbers and acanthosis compared to all animals. Finally, increases in the number of cutaneous nerves were found in all transgenic mice compared to littermate controls.

Conclusion

These findings demonstrate that change to one system (vascular or epidermal) results in change to other cutaneous systems and suggest that individual molecules can exert effects on multiple systems.     

Cathepsin K-upregulation in fibroblasts promotes matrigel invasive ability of squamous cell carcinoma cells via tumor-derived IL-1α

Background

Cathepsin K (CTSK), a cysteine protease with strong collagenolytic properties, is involved in extracellular matrix turnover. In the previous studies, CTSK expression was detected in peritumoral fibroblasts (Fbs) around squamous cell carcinoma (SCC), but not in those surrounding benign epidermal tumors. However, the mechanism governing CTSK expression in epidermal tumors remains unclear.

Objective

To study the regulatory mechanisms of fibroblastic CTSK expression in the SCC-stromal interaction.

Methods

We examined dynamic interactions of Fbs with tumorigenic SCC cells (A431 and A253) or normal human keratinocytes.

Results

SCC cells and normal keratinocytes did not synthesize CTSK, while Fbs constitutively expressed CTSK. When cocultured, SCC cells upregulated fibroblastic CTSK expression more potently than did normal keratinocytes, which was mainly attributable to SCC-derived IL-1α. Coculturing Fbs with SCC cells significantly augmented the matrigel invasive ability of SCC cells, which was downregulated when cocultured with CTSK knockdown Fbs or in the presence of neutralizing anti-IL-1α antibody.

Conclusion

The CTSK-upregulated Fbs generated by SCC-derived IL-1α may play a crucial role in the progression and invasion of SCC.     

Benzo[c]phenanthridine alkaloids exhibit strong anti-proliferative activity in malignant melanoma cells regardless of their p53 status

Background

Search for new substances with antiproliferative activity towards melanoma cells is important since malignant melanoma is notoriously resistant to conventional chemotherapy. Benzo[c]phenanthridine alkaloids (BAs) are natural products with significant anti-proliferative activities, therefore they are considered as agents promising for cancer therapy.

Objectives

The effects of five BAs (sanguinarine, chelerythrine, chelidonine, sanguilutine, and chelilutine) on human malignant melanoma cell lines were compared. The study focused on BAs effects on DNA, anti-apoptotic and p53 protein levels; and the involvement of p53 in cellular responses to alkaloids treatment.

Methods

Melanoma cell lines, two wild types and two with dysfunctional p53 derived from one of them were used. The mechanism of anti-proliferative and pro-apoptotic effects and the effect on DNA was investigated using MTT assay, flow cytometry, Western blot analysis, fluorescence and electron microscopy.

Results

All tested alkaloids exhibit strong anti-proliferative activity. CHL, CHE and SA induced apoptosis, which was probably mediated by decreasing levels of anti-apoptotic proteins (Bcl-xL, Mcl-1, XIAP) and was accompanied by mitochondrial membrane potential decrease as well as caspase-3 and PARP cleavage. Although all alkaloids caused DNA damage, which was demonstrated by induction of H2AX phosphorylation, none of the tested alkaloids stabilised p53 and their toxicity in cells with non-functional p53 was comparable to wild type cells.

Conclusion

Despite the profound similarity of BAs molecular structures, it is clear that the mechanism of cell death induction is different for each alkaloid. Our results indicate that BAs could be effective in malignant melanoma treatment, including tumours which have lost wild type p53.     

Differential modulation of stress-inflammation responses by plant polyphenols in cultured normal human keratinocytes and immortalized HaCaT cells

Background

Environmental and endogenous stresses to skin are considered causative reasons for skin cancers, premature ageing, and chronic inflammation. Screening of substances with preventive and/or curative properties is currently based on mechanistic studies of their effects towards stress-induced responses in skin cell cultures.

Objective

We compared effects of plant polyphenols (PPs) on the constitutive, UVA-, LPS-, or TNF-alpha-induced inflammatory responses in cultured normal human epidermal keratinocytes (NHEK) and immortalized HaCaT cells.

Methods

Representatives of three classes of PPs, flavonoids, stilbenoids, and phenylpropanoids were studied. Their effects on mRNA were determined by qRT-PCR; protein expression was assayed by Western blot and bioplexed ELISA; phosphorylation of Akt1, ERK1/2, EGFR, and NFkappaB was quantified by intracellular ELISA or Western blot.

Results

PPs or their combination with UVA or LPS induced strong up-regulation of stress responses in HaCaT but not in NHEK. In addition, compared to NHEK, HaCaT responded to TNF-alpha with higher synthesis of MCP-1, IP-10 and IL-8, concomitant with stronger NFkappaB activation. PPs down-regulated the chemokine release from both cell types, although with distinct effects on NFkappaB, Akt1, ERK, and EGFR activation.

Conclusion

Results of pharmacological screenings obtained by using HaCaT should be cautiously considered while extending them to primary keratinocytes from human epidermis.     

Comparison of the antimelanogenic effects of p-coumaric acid and its methyl ester and their skin permeabilities

Background

p-Coumaric acid (PCA) inhibits human tyrosinase (TYR) activity and melanin synthesis in human epidermal melanocytes.

Objective

The purpose of the current study was to examine the potential of PCA and its hydrophobic derivative, methyl p-coumarate (MPC), as hypopigmenting agents for topical use.

Methods

PCA and MPC were comparatively tested against in vitro human TYR enzyme activity and cellular melanin synthesis in human epidermal melanocytes. Permeation studies were undertaken using an artificial lipophilic membrane and an excised porcine skin. In vivo hypopigmenting efficacy was assessed on the skin of melanin-possessing hairless mice exposed to UVB.

Results

Although PCA was a stronger inhibitor than MPC against TYR activity in vitro, the former inhibited cellular melanin synthesis less effectively than the latter. A non-cell based permeability assay indicated that PCA was practically impermeable through the lipophilic barrier while MPC was highly permeable. In contrast, an ex vivo skin permeation study demonstrated that topically applied PCA in the form of a cream can diffuse into the aqueous medium underneath the skin. No MPC was released from a MPC cream but PCA was released instead as a bio-converted product. Topical application of PCA cream attenuated the UVB-induced erythema formation and pigmentation in mice models, more effectively compared with MPC cream.

Conclusion

PCA may be useful as an active ingredient for topical applications for a hypopigmenting effect. MPC has potential as a hypopigmenting agent but requires rather invasive methods for its delivery to the target cells.     

Semaphorin 7A on keratinocytes induces interleukin-8 production by monocytes

Background

Semaphorin 7A (Sema7A) expressed on activated T cells stimulates cytokine production in monocytes through its receptor, α1β1 integrin.

Objective

To study the significance of Sema7A expressed on keratinocytes in skin inflammation where interaction between keratinocytes and β1-integrin expressing inflammatory cells, such as monocytes, takes place.

Methods

The regulation of Sema7A expression on keratinocytes by various cytokines was studied by flow cytometry and immunoblot. β1-integrin expressing human monocyte cell line, THP-1 cells, were co-cultured with paraformaldehyde-fixed normal human epidermal keratinocytes (NHK) and IL-8 production by THP-1 cells was studied. The significance of β1-integrin or Sema7A within this cell interaction was examined by the experiments using β1-integrin blocking antibody or Sema7A siRNA.

Results

IFN-γ and TNF-α slightly increased Sema7A expression, while IL-4 decreased it. Among cytokines tested, TGF-β1 most strikingly increased the Sema7A expression on NHK. When NHK was stimulated by TGF-β1, paraformaldehyde-fixed, and co-cultured with THP-1 cells, IL-8 production by THP-1 cells was increased compared to THP-1 cells only. When THP-1 cells were pretreated with β1-integrin blocking antibody, this increase in IL-8 production by THP-1 cells was inhibited. Likewise, when NHK were pretreated with Sema7A siRNA before fixation and co-cultured with THP-1 cells, increase in IL-8 production by THP-1 cells was inhibited.

Conclusion

Our results suggest that Sema7A on keratinocytes and β1-integrin on monocytes contribute to monocyte activation by keratinocytes within skin inflammation, such as psoriasis or wound.     

New insights into the mechanism of abnormal calcification in nephrogenic systemic fibrosis - gadolinium promotes calcium deposition of mesenchymal stem cells and dermal fibroblasts

Background

Recent studies have suggested that there is a close association between the administration of gadolinium (Gd)-based contrast agents and the development of nephrogenic systemic fibrosis (NSF), an acquired disorder characterized by systemic fibrosis and abnormal calcification in patients with severe renal dysfunction. However, the causative roles of Gd remain unknown.

Objective

The aim of this in vitro study was to investigate the effect of Gd on the development of fibrosis and calcification in cultured cells.

Methods

MC3T3-E1 cells (pre-osteoblastic cells), human adipose tissue-derived mesenchymal stem cells (HAMSCs), human subcutaneous preadipocytes, and human dermal fibroblasts (HDFs) were each cultured in differentiation medium with or without gadolinium chloride. Calcium deposition of MC3T3-E1 cells, HAMSCs, and HDFs was determined by alzarin red S staining. Adipogenic differentiation of human subcutaneous preadipocytes and HAMSCs was determined by oil red O staining. Fibrogenesis of HDFs was determined by real-time PCR to measure the mRNA expression of type I collagen. Cell proliferation was determined by MTS assay.

Results

Gd induced calcium deposition in MC3T3-E1 cells, HAMSCs and HDFs in osteogenic differentiation media. Gd did not induce adipogenic differentiation in human subcutaneous preadipocytes and HAMSCs. Gd did not increase the mRNA expression of type I collagen in HDFs, but did promote cell proliferation.

Conclusions

We have demonstrated a direct effect of Gd on calcium deposition in cultured cells. The result will help us to understand the mechanism of abnormal calcification in NSF.     

The hsp27kD heat shock protein and p38-MAPK signaling are required for regular epidermal differentiation

Background

In human epidermal keratinocytes the expression of hsp27 is closely related to differentiation in vitro and in situ.

Objective

We aimed to gain further insight into the role of hsp27 in epidermal differentiation by specific inhibition through siRNA and inhibition of p38-MAPK, the key enzyme of hsp27 phosphorylation.

Methods

Normal human keratinocytes (KC) and organotypic skin cultures (SE-skin equivalents) were used. Expression and phosphorylation of hsp27 was inhibited in these models by siRNA and SB203580, a specific inhibitor of p38-MAPK, respectively. Modification of morphology and expression of hsp27 and other differentiation associated proteins was investigated by immunofluorescence, western blot, and RT-PCR.

Results

Inhibition of p38-MAPK resulted in a downregulation of hsp27 in KC and SE. Additionally, in the presence of SB203580 Ca²⁺ induced expression of pro-filaggrin and loricrin was inhibited at the protein level and expression of filaggrin, keratin 10, and transglutaminase 1 at the mRNA level. Addition of SB203580 to SE, as well as hsp27 knockdown in this model resulted in identical patterns of irregular differentiation, disturbance of epidermal layers, and delayed expression of K10.

Conclusion

These results provide evidence that the expression of hsp27 and its phosphorylation by p38-MAPK are required for keratinocyte differentiation and for the formation of a regularly stratified epidermis.     

Analysis of cell characterization using cell surface markers in the dermis

Background

In recent years, it has been reported that stem cells exist in the mesenchymal tissues of the bone marrow and adipose. These stem cells are thought to express specific cell surface markers such as CD44, CD54, CD105, CD90, and CD271 and have been confirmed to be pluripotent. Furthermore, although it has been reported that stem cells are also present in the dermis, their cell surface markers and characteristics are not fully understood.

Objective

To confirm the presence of stem cells in the dermis and their ability, employing the mesenchymal stem cell markers which have previously been reported as an indication.

Methods

We analyzed the percentages of CD44 (+), CD54 (+), CD90 (+), CD105 (+), and CD271 (+) cells in the dermis of neonatal mice (HR-1 mouse) by performing immunostaining and FACS. Secondly, we isolated each type of marker-positive and -negative cells from dermal tissues and evaluated their proliferation potential and their ability to differentiate into adipocytes, osteoblasts, and chondrocytes.

Results

According to the immunostaining and FACS results, we confirmed that stem cells that express CD44, CD54, CD90, CD105, and CD271 are present in the dermal tissues of neonatal mice. In addition, when we measured the proliferation and differentiation potentials of each type of marker-positive cells, it was revealed that cells expressing CD54 or CD271 have a high proliferation potential and are able to differentiate into adipocytes, osteoblasts, and chondrocytes.

Conclusions

These results indicated that dermal tissues contain stem cells that express CD44, CD54, CD90, CD105, and CD271 which are stem cell markers. More precisely, it was suggested that both CD54 (+) and CD271 (+) stem cells have high proliferation and differentiation potentials.     

Expression of antimicrobial peptides in diabetic foot ulcer

Background

Foot ulcers are one of the main diabetes complications due to its high frequency and difficulty of complete healing. There are several factors that participate in diabetic ulcers development and limited information exists about the role of antimicrobial peptides (AMP) in its pathogenesis.

Objective

The aim of this study was to analyze the expression pattern of the main AMPs: Human Neutrophil Peptide (HNP)-1, Human β-defensin (HBD)-1, HBD-2, HBD-3, HBD-4 and cathelicidin LL-37 in biopsies from diabetic foot ulcers (DFU).

Methods

20 biopsies from DFU grade 3 according to Wagner's classification and 20 biopsies from healthy donors were obtained. Real time PCR, immunohistochemistry and primary cell cultures were performed.

Results

β-Defensins were overexpressed in DFU, whereas LL-37 has low or none expression in comparison with healthy skin. When primary cell culture from these biopsies were performed and infected with Staphylococcus aureus, epidermal cell from diabetic ulcers showed lower LL-37 expression compared with cell cultures from healthy donors skin.

Conclusion

These results suggest that though most AMPs are expressed in DFU, this production is not appropriate to promote wound healing and contain secondary infections.     

EC-SOD induces apoptosis through COX-2 and galectin-7 in the epidermis

Background

Extracellular superoxide dismutase (EC-SOD) is an anti-oxidant enzyme found in the extracellular matrix of tissues, and plays an important role in the prevention of many diseases caused by oxidative stress. However, other functions of EC-SOD in epidermis are not well known.

Objective

We investigated the functions of EC-SOD in epidermis using keratinocyte cell line and EC-SOD transgenic mice.

Methods

Expression of galectin-7 in pEC-SOD transfected cells or skin of EC-SOD transgenic mice was detected by western blot analysis. The percentage of apoptotic cells was determined by propidium iodide staining and subsequent FACS analysis. COX-2 siRNA or scrambled siRNA was transfected into HaCaT cells and western blot analysis was performed to detect pro-apoptotic protein levels.

Results

The epidermis of EC-SOD transgenic mice was thinner than wild type mice. In addition, we showed that the thin epidermis of EC-SOD transgenic mice results from the apoptosis of epidermal cells. To elucidate which molecules are involved in EC-SOD-induced apoptosis, we utilized two-dimensional electrophoresis; the results showed that the epidermis of EC-SOD transgenic mice produces more galectin-7, a pro-apoptotic factor, than the wild type. Furthermore, we showed that the transfection of EC-SOD-expressing plasmids induces the production of galectin-7, and pro-apoptotic proteins in keratinocytes. This suggests that EC-SOD induces apoptosis through increased galectin-7 expression. Finally, we demonstrated that EC-SOD-induced galectin-7 results from the production of COX-2.

Conclusion

Our results imply that EC-SOD plays a role not only as a reactive oxygen species scavenger, but also as a pro-apoptotic factor via COX-2/galectin-7 pathways in the epidermis.     

Phenylbutyrate suppresses distinct skin reactions that are enhanced by blockade of epidermal growth factor receptor signaling

Background

Epidermal growth factor receptor inhibitors (EGFRIs) cause skin inflammation, and understanding the factors that mediate this reaction is fundamental for designing therapies for EGFRI-related cutaneous side effects.

Objective

We characterized EGFRI-enhanced skin reactions and evaluated the therapeutic efficacy of phenylbutyrate, a histone deacetylase inhibitor.

Methods

PD168393, an EGFRI, was applied topically to the ear skin of mice with or without mast cell deficiency. The skin was then irritated once or pre-sensitized and repeatedly challenged with 2,4-dinitrofluorobenzene (DNFB). The reaction pattern, the type and number of infiltrating cells, changes in protein, cytokine (TNF-α) and chemokine (CCL2) expression, and the immune response were analyzed. Phenylbutyrate, formulated as a gel for topical treatment or dissolved in water for intraperitoneal administration, was tested as a treatment.

Results

EGFRI rapidly upregulated the mast cell chemotactic factor, stem cell factor (SCF) and augmented DNFB-induced immediate contact dermatitis within hours of treatment in the presence of mast cells. Topical phenylbutyrate treatment suppressed EGFRI-induced SCF expression in the epithelium, inhibited DNFB-induced mast cell recruitment in the dermis, and ameliorated the EGFRI-enhanced acute skin reaction. EGFRI also enhanced the delayed-type DNFB-induced hypersensitive reaction that was mast-cell independent but was associated with T lymphocytes. Systemic phenylbutyrate administration suppressed EGFRI-enhanced delayed-type skin hypersensitivity by increasing the number and function of Foxp3⁺ T regulatory suppressor cells, which inhibited T helper cell proliferation.

Conclusions

Our data suggest that phenylbutyrate has dual beneficial therapeutic effects on EGFRI-enhanced acute (local inflammatory) and late (systemic immune) skin reactions.     

Differentiation-dependent expression of NADP(H):quinone oxidoreductase-1 via NF-E2 related factor-2 activation in human epidermal keratinocytes

Background

NADP(H):quinone oxidoreductase-1 (NQO-1) is known for its protective role in skin carcinogenesis, but the expression of NQO-1 during keratinocyte (KC) differentiation has not been studied.

Objective

The purpose of the current study was to evaluate modulation of NQO-1 and NF-E2-related factor-2 (Nrf2) during KC differentiation.

Methods

Normal human epidermal keratinocytes (NHEKs) were induced to differentiation by prolonged culture after confluency (postconfluence).

Results

NQO-1 was induced at the late stage of differentiation of NHEKs (7th day of postconfluence). The expression of postconfluence-induced NQO-1 was stimulated by 0.1 mM H₂O₂, but attenuated by 5 mM N-acetylcysteine, implying that reactive oxygen species (ROS) are implicated in the expression of NQO-1 in differentiated KCs. Nrf2 was up-regulated at the earlier than NQO-1 induction (3rd day of postconfluence). The Nrf2-dependent expression of NQO-1 was further supported by Nrf2-siRNA experiments. A confocal study confirmed the differentiation-dependent induction and activation of NOQ-1 and Nrf-2 in NHEKs. Immunohistochemistry showed that NQO-1 was accentuated in the upper epidermal layers, supporting the notion that differentiation-dependent NQO-1 expression is functional in human skin in vivo.

Conclusion

These results demonstrate that NQO-1 is modulated during KC differentiation via Nrf2 pathway, suggesting the active role of NQO-1 in the differentiating epidermis.     

L-3-Phosphoserine phosphatase (PSPH) regulates cutaneous squamous cell carcinoma proliferation independent of L-serine biosynthesis

Background

l-3-Phosphoserine phosphatase (PSPH) is a highly conserved and widely expressed member of the haloacid dehalogenase superfamily and the rate-limiting enzyme in l-serine biosynthesis. We previously found Psph expression to be uniquely upregulated in a α6β4 integrin transgenic mouse model that is predisposed to epidermal hyperproliferation and squamous cell carcinoma (SCC) formation implicating a role for Psph in epidermal homeostasis.

Objective

We examined the status of PSPH in normal skin epidermis and skin tumors along with its sub-cellular localization in epidermal keratinocytes and its requirement for squamous cell carcinoma (SCC) proliferation.

Methods

First, an immunohistochemical study was performed for PSPH in normal skin and skin cancer specimens and in cultured keratinocytes. Next, biochemical analyses were performed to confirm localization of PSPH and to identify candidate binding proteins. Finally, proliferation and apoptosis studies were performed in human SCC and normal keratinocytes, respectively, transduced with vectors encoding small hairpin RNAs targeting PSPH or overexpressing a phosphatase-deficient PSPH mutant.

Results

PSPH is expressed throughout the proliferative layer of the epidermis and hair follicles in rodent and human skin and is highly induced in SCC. In keratinocytes, PSPH is a cytoplasmic protein that primarily localizes to endosomes and is present primarily as a homodimer. Knock down of PSPH dramatically diminished SCC cell proliferation and cyclin D1 levels in the presence of exogenous of l-serine production suggesting a non-canonical role for PSPH in epithelial carcinogenesis.

Conclusions

Psph is highly induced in proliferative normal keratinocytes and in skin tumors. PSPH appears to be critical for the proliferation of SCC cells; however, this phenomenon may not involve the phosphoserine metabolic pathway.     

Skin tumor formation in human papillomavirus 8 transgenic mice is associated with a deregulation of oncogenic miRNAs and their tumor suppressive targets

Background

Dysregulation of microRNA (miRNA) expression is regularly found in various types of cancer and contributes to tumorigenic processes. However, little is known about miRNA expression in non-melanoma skin cancer in which a pathogenic role of beta human papillomaviruses (HPV) is discussed. A carcinogenic potential of beta HPV8 could be demonstrated in a transgenic mouse model, expressing all early genes of HPV8 (HPV8-CER). A single UVA/B-dose induced oncogene expression and led to papilloma growth within three weeks.

Objective

Expression of miRNAs and their targets during HPV8-mediated tumor formation in mice.

Methods

Skin of untreated or UV-irradiated wild-type and HPV8-CER mice was analyzed for miRNA expression and localization by qPCR and in situ hybridization. MiRNA target protein expression was analyzed by immunohistochemical staining.

Results

Early steps in skin tumor formation in HPV8-CER mice were associated with an upregulation of the oncogenic miRNA-17-5p, -21 and -106a and a downregulation of the tumor-suppressive miRNA-155 and -206, which could be demonstrated by qPCR and in situ hybridization. The respective targets of miRNA-21 and -106a, the tumor suppressors PTEN, PDCD4 and Rb with their pivotal role in cell cycle regulation, apoptosis and proliferation were found to be downregulated.

Conclusion

This is the first report demonstrating that a cutaneous HPV type deregulates the expression of miRNAs. These deregulations are closely related to the UV-induced upregulation of HPV8 oncogene levels, which suggest a direct or indirect HPV8-specific effect on miRNA expression. These data presume that HPV8 interferes with the miRNA mediated gene regulation to induce tumorigenesis.     

The flavonoids apigenin and luteolin suppress ultraviolet A-induced matrix metalloproteinase-1 expression via MAPKs and AP-1-dependent signaling in HaCaT cells

Background

Ultraviolet (UV) irradiation causes major changes in skin connective tissues as a result of the degradation of collagen, a major structural component of the extracellular matrix. This process is likely mediated by matrix metalloproteinases (MMPs). Such changes in collagenous skin tissues have been suggested to be causes of cutaneous aging and skin cancer.

Objective

We investigated the protective effects of apigenin and luteolin on immortalized human keratinocytes (HaCaT) against UVA damage. We then explored the inhibitory effects of apigenin and luteolin on UVA-induced MMP-1 and investigated the molecular mechanism underlying those effects.

Methods

HaCaT cells were treated with apigenin and luteolin for the indicated times followed by irradiation with UVA. Those effects were assessed by semi-quantitative PCR, Western blotting and enzymic activity assays.

Results

These two compounds, at concentrations of 1-5 μM, increased the viability of, and inhibited ROS production in HaCaT cells exposed to UVA irradiation. Pre-treatment of HaCaT cells with apigenin and luteolin also inhibited UVA-induced production of the collagenases MMP-1. They also suppressed UVA-induced expression of c-Jun and c-Fos and the phosphorylation of three MAP kinases, upstream modulators of AP-1. Furthermore, the same two flavonoids decreased the UVA-induced influx of Ca²⁺ into HaCaT cells and the phosphorylation of Ca²⁺/calmodulin-dependent kinases (CaMKs).

Conclusion

The results indicate that apigenin and luteolin inhibited UVA-induced collagenolytic MMP-1 production by interfering with Ca²⁺-dependent MAPKs and AP-1 signaling. They may thus be potentially useful in the prevention and treatment of skin photoaging.     

Interactions between myofibroblast differentiation and epidermogenesis in constructing human living skin equivalents

Background

During skin wounding and healing, skin homeostasis is interrupted. How the altered epithelial-mesenchymal interactions influence scar formation and epidermogenesis should be investigated using three-dimensional models that are similar to in vivo structures.

Objective

In this study, we assessed the effects of epithelial-mesenchymal interactions on myofibroblast differentiation and how myofibroblasts influence epidermogenesis using a human living skin equivalent (LSE) model.

Methods

We constructed a fibroblast-populated type I collagen gel upon which LSEs were formed by seeding with normal human keratinocytes. Samples of the collagen gel and LSEs were collected at different time points. Myofibroblast differentiation, epidermal differentiation, and proliferation status were investigated immunohistochemically. Several measures were taken to suppress α-smooth muscle actin (α-SMA) expression to determine the effects of myofibroblasts on epidermogenesis, including the addition of basic fibroblast growth factor or a transformation growth factor-β (TGF-β) kinase inhibitor to the culture medium and the inclusion of an amniotic membrane (AM) in the dermal matrix.

Results

The myofibroblast/fibroblast ratio in the fibroblast-populated collagen gel kept rising during culture. In the LSEs, most fibroblasts were α-SMA-negative, except for those along the dermal-epidermal junction. The suppression of α-SMA expression enhanced epidermal differentiation and decreased TGF-β1 expression in the epidermis. The inhibition of TGF-β kinase completely suppressed α-SMA expression in the dermal matrix.

Conclusions

Epidermogenesis suppressed α-SMA expression in the fibroblast-rich dermal matrix, except near the dermal-epidermal junction. The α-SMA-positive cells at the dermal-epidermal junction contributed to the hyperproliferative phenotype of the epidermis. In contrast, the hyperproliferative epidermis expressed more TGF-β1, which is responsible for myofibroblast differentiation.     

Optimization of filaggrin expression and processing in cultured rat keratinocytes

Background

In normal mammalian epidermis, cell division occurs primarily in the basal layer where cells are attached to the basement membrane. Upon release from the basement membrane, these basal cells stop dividing and begin to differentiate and stratify producing cornified cells expressing differentiation markers, including the keratin bundling protein filaggrin, and cornified envelope proteins. Little is understood about the regulatory mechanisms of these processes. A rat epidermal keratinocyte cell line synthesizing and processing profilaggrin at confluence in a synchronous manner for 4-5 days provides a useful culture model for epidermal differentiation. Profilaggrin expression in this cell line however decreases with passaging, and its processing involves extensive nonspecific proteolysis.

Objective

Our objective was to identify culture conditions that effect the decrease in profilaggrin expression with passaging and nonspecific proteolysis of profilaggrin in order to study epidermal differentiation more closely.

Method

The large amount of nonspecific proteolysis suggested autophagocytosis. To test this, cells were cultured in the presence of 3-methyladenine (3-MA). Two known gradients in epidermis are decreasing serum components and increasing calcium concentrations in the upper cell layers. To determine whether these gradients effected processing, cells were cultured in serum/DMEM or in serum-free KGM and under varying external calcium concentrations. Cells were also cultured in presence of aminoguanidine in an attempt to maintain profilaggrin expression with passaging.

Results

Profilaggrin expression was enhanced in the presence of 3-MA, with optimum around 6 mM. In the absence of aminoguanidine, profilaggrin expression decreased as a function of increasing passage number; in its presence, profilaggrin expression remained high in some, but not in all of the independently maintained cell lines. Thus, culturing in aminoguanidine was necessary, but not sufficient, for sustained ability to express profilaggrin at confluence. Production of filaggrin from profilaggrin was maximized in a serum-free medium with [Ca²⁺] at 5 mM. Filaggrin associates with phospholipid vesicles in vitro forming aggregates similar to those seen in vivo, suggesting that filaggrin release induces vesicular aggregation and autophagocytosis.

Conclusion

We have used a keratinocyte cell line that synthesizes and processes profilaggrin after confluence as a culture model to study epidermal differentiation. In this system profilaggrin processing must be preceded by inhibition of autophagosome formation and/or modulation of vesicular trafficking, and these processes are regulated by epidermal calcium and serum factor gradients.     

Visualization and characterisation of defined hair follicle compartments by Fourier transform infrared (FTIR) imaging without labelling

Background

To visualise and characterise skin architecture, the tissue usually has to be destroyed and labelled.

Objectives

The use of Fourier transform infrared (FTIR) spectroscopy as a label-free, minimally sample destructive method to define hair follicular structure has been explored and demonstrated in this paper.

Methods

Human scalp skin cryosections were imaged using FTIR microscopy and the data was subsequently analysed with N-FINDR spectral unmixing algorithm.

Results

This resulted in an excellent distinction of known hair follicle tissue layers, which could be discerned based on their molecular structure.

Conclusion

The development of a minimally sample-destructive, label-free spectroscopy based technique that can differentiate layers of cells in the dermal papilla and connective tissue sheath in the mesenchyme of the hair follicle paves the way forward to identifying spectral markers important in wound healing and stem cell therapies.